Given the task definition and input, reply with output. In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D". 

[header] How to choose and install a doggie door [title] Consider door mounts. [step] Door mounts are doggie doors that are installed onto doors in your home. These can be placed on exterior doors to allow your dog to easily travel inside or outside. <sep> (A) The corral-style mounts tend to have fewer features as they are easily discussed in a later step. The main feature is having a door mount on your door. (B) [substeps] If your dog has sensitive ears, a door mount might be necessary if you plan to use a doggie door at night. If your dog will be outside overnight, they will need access to inside animals' homes at all times. (C) They can also by placed on internal doors, to allow your dog to access certain rooms in your home. Door mounts can be added to wooden, aluminum, or screen doors and typically consist of a swinging flap door. (D) You can also install screen or plastic panels on a front or rear door for a doggie door stand. There are window mounts that provide your dog with better ventilation, enhancing your doggie door.

C